With PV2010 and "linear" ACR settings one does get linear results and this enables one to produce a scene referred image using the method outlined by the ICC. It is really a nightmare to get such results in PV2012...

I used the Adobe Standard calibration for my work. One could look at the tone curve in the DNG profile editor, but that is for another day.

As far as I can tell from some qualitative tests, we can still get close to a linear, scene-referred rendition by creating a custom color profile with the DNG Profile Editor with its Tone Curve set to Linear, then using Camera Raw Defaults (whether with PV 2010 or 2012) when processing the image with that custom profile selected. Some limited deviations being due to auto-highlight-recovery and the auto-black-point functionality coming into play with PV 2012, depending on image.

As for PV 2010 the results with this approach of using a linear profile are indeed nearly identical compared to "linear" ACR settings (basic sliders zero'd and Point Curve = Linear) while using a profile with Camera Raw Default Tone Curve... as confirmed earlier by Eric.

As far as I can tell from some qualitative tests, we can still get close to a linear, scene-referred rendition by creating a custom color profile with the DNG Profile Editor with its Tone Curve set to Linear, then using Camera Raw Defaults (whether with PV 2010 or 2012) when processing the image with that custom profile selected. Some limited deviations being due to auto-highlight-recovery and the auto-black-point functionality coming into play with PV 2012, depending on image.

As for PV 2010 the results with this approach of using a linear profile are indeed nearly identical compared to "linear" ACR settings (basic sliders zero'd and Point Curve = Linear) while using a profile with Camera Raw Default Tone Curve... as confirmed earlier by Eric.

Peter,

I compared the PV2010 linear (linear point curve, sliders on main tab all zero) with a custom profile with a linear tone curve created in the DNG profile editor and defaults in PV2012. The results are nearly the same except for some divergence in the highlights and a bit greater divergence in the shadows, consistent with your predictions. It is really easier to use the PV2010 method and not have to make a custom profile and worry about highlights and shadows. A log-log plot is necessary to obtain a linear curve with gamma encoded images.

I compared the PV2010 linear (linear point curve, sliders on main tab all zero) with a custom profile with a linear tone curve created in the DNG profile editor and defaults in PV2012. The results are nearly the same except for some divergence in the highlights and a bit greater divergence in the shadows, consistent with your predictions. It is really easier to use the PV2010 method and not have to make a custom profile and worry about highlights and shadows.

Bill,

When creating a linear custom profile by means of the Profile Editor, one interesting observation by the way wasthat the initial Tone Curve as introduced by the Base Profile = Adobe Standard is noticeably different from Tone Curve set to Camera Raw Default. The latter and the resulting profile are supposed to be the more correct choice for linearizing PV 2010 the old way (w/ basic controls zero’d and Point Curve Linear). It also minimizes the difference compared to PV 2010 or PV 2012 @ default settings while using a linear custom profile. It may depend though on the camera and the corresponding Adobe Standard profile, however, it seems that we have always been in need of a custom profile for the given task.

When creating a linear custom profile by means of the Profile Editor, one interesting observation by the way wasthat the initial Tone Curve as introduced by the Base Profile = Adobe Standard is noticeably different from Tone Curve set to Camera Raw Default. The latter and the resulting profile are supposed to be the more correct choice for linearizing PV 2010 the old way (w/ basic controls zero’d and Point Curve Linear). It also minimizes the difference compared to PV 2010 or PV 2012 @ default settings while using a linear custom profile. It may depend though on the camera and the corresponding Adobe Standard profile, however, it seems that we have always been in need of a custom profile for the given task.

For my camera the Adobe Standard profile and its tone curve produce linear results with PV2010 when the basic controls are zeroed and the point curve is set to linear as shown below. The departure from linearity in the deep shadows is likely due to flare light. It certainly does no harm to make a custom curve in the DNG profile editor using the linear tone curve option which overrides whatever tone curve is present in the base profile.

In my experience it is very difficult to produce linear results with PV2012, consistent with Bart's observations. Have you succeeded?

For my camera the Adobe Standard profile and its tone curve produce linear results with PV2010 when the basic controls are zeroed and the point curve is set to linear as shown below. The departure from linearity in the deep shadows is likely due to flare light.

That's a quite perfect result, Bill.

Out of interest, does the Adobe Standard profile for your camera show any difference between Tone Curve = Base Profile vs. Camera Raw Default in the DNG Profile Editor ?

In my experience it is very difficult to produce linear results with PV2012, consistent with Bart's observations. Have you succeeded?

For my qualitative purposes, and also in view of the close match seen with the graph in your previous post # 22, I’d say that the linear results with PV 2012 are reasonably okay. We could argue that an (auto-)black-point setting does not per se break linearity in the sense of y= ax + b (although the new implementation of Blacks may have overcome such simple math), and further that the auto-highlight recovery feature seems to act quite gentle, and is virtually without effect with a properly exposed image. Just as you stated "The results are nearly the same except for some divergence in the highlights and a bit greater divergence in the shadows".

I agree that Charles Cramer's post is masterful and very useful. In my own analysis of PV2012 I used a 40 step wedge, whereas Charles used a 20 step wedge. In the 40 step wedge the steps are in 0.3 optical density decrements, so 3 steps equals 1 f/stop. The values of the wedge are shown below, where step 1 has an OD of 0.05, placing it at the values shown. Step 8 is neutral gray.

Not that it matters but....0.30 density = 1 f/stop. The scale in question has increments of 0.10 which is 1/3 stop.....so 3 steps = 1 f/stop as you stated.

I'm curious how the Stouffer transmission scale was photographed. You used a transparency/slide viewer? What sort of surround did you use to reduce flare? Black/opaque, gray or no surround?

I'm curious how the Stouffer transmission scale was photographed. You used a transparency/slide viewer? What sort of surround did you use to reduce flare? Black/opaque, gray or no surround?

Very informative by the way....thanks for doing all the hard work

I used a 5000K light box formerly used for viewing transparencies (left over from my film days). I did replace the magnetic ballast with electronic to avoid 60hz flicker. Masking off the surround is critical and I used exposed x-ray film supplied by a radiologist friend. It is thin and quite opaque, but is getting harder to get since digital is also taking over medical imaging.